Short-chain dehydrogenases (SCDs) are a family of dehydrogenases that share only 15% to 30% sequence identity, with similarity predominantly in the coenzyme binding domain and the substrate binding domain. In addition to their role in detoxification of ethanol, SCDs are involved in synthesis and degradation of fatty acids, steroids, and some prostaglandins, and are therefore implicated in a variety of disorders, such as lipid storage disease, myopathy, SCD deficiency, and certain genetic disorders.
The SCD, 15-hydroxy-prostaglandin dehydrogenase (15-PGDH), (hydroxyprostaglandin dehydrogenase 15-(nicotinamide adeninedinucleotide); 15-PGDH; Enzyme Commission number 1.1.1.141; encoded by the HPGD gene), represents the key enzyme in the inactivation of a number of active prostaglandins, leukotrienes and hydroxyeicosatetraenoic acids (HETEs) (e.g., by catalyzing oxidation of PGE2 to 15-keto-prostaglandin E2, 15 k-PGE). The human enzyme is encoded by the HPGD gene and consists of a homodimer with subunits of a size of 29 kDa. The enzyme belongs to the evolutionarily conserved superfamily of short-chain dehydrogenase/reductase enzymes (SDRs), and according to the recently approved nomenclature for human enzymes, it is named SDR36C1. Thus far, two forms of 15-PGDH enzyme activity have been identified, NAD+-dependent type I 15-PGDH that is encoded by the HPGD gene, and the type II NADP-dependent 15-PGDH, also known as carbonyl reductase 1 (CBR1, SDR21C1). However, the preference of CBR1 for NADP and the high Km values of CBR1 for most prostaglandin suggest that the majority of the in vivo activity can be attributed to type I 15-PGDH encoded by the HPGD gene, that hereafter, and throughout all following text, simply denoted as 15-PGDH.